1. Field of the Invention
The present invention relates to devices for obtaining samples from moving fluids, such as rivers, streams, pipes, sewers, or irrigation canals.
Water sampling is essential to proper development and management of water and land resources. The need for a clear understanding of the effects of hydro-geomorphologic processes has become increasingly important. Processes such as erosion and fluvial transport of sediment and other associated constituents (xe2x80x9cloadsxe2x80x9d), require accurate measurement of sediment and constituent content within bodies of water. Stream flow and constituent loads are the most important data collected for such an analysis and require flow measurements and water quality sample collection for determining representative concentrations of the constituents of interest. Some of the constituents of interest are suspended solids, phosphorous, nitrogen, and heavy metals. But, natural environmental factors such as geology, soils, climate, runoff, topography, drainage area, and ground cover make obtaining samples and data challenging. For example, in remote forests areas it has become important to monitor runoff to streams and rivers to determine the effects of logging, but obtaining reliable test samples is difficult.
Current monitoring of the hydro-geomorphic processes in stream locations is conducted either by xe2x80x9cgrab samplingxe2x80x9d or by automated samplers. Manual grab samples, which usually provide accurate samples and flow measurements, have the disadvantages of requiring frequent trips to the test site and providing no guarantee of sampling during a runoff event. Current automated devices are versatile in that they are capable of sampling on a programmable time basis or a proportional stream flow basis, and therefore are able to sample during runoff events. Some of the major disadvantages of automated samplers are that they are expensive, use substantial power and require frequent battery charging or expensive and complicated alternative power supplies. Owing to the need to re-charge batteries, automated samplers require frequent attention, which is difficult to provide in remote locations. Moreover, owing to the automated samplers"" expense and complexity, users are reluctant to leave them unattended in remote locations, for fear they will be stolen or vandalized. Consequently, there is a need for a simple, inexpensive, flow-proportional sampler that can obtain accurate samples.
To obtain samples and data, and to test and monitor moving fluids, such as streams, there is a need for a sampler that can take adjustable volume samples or samples based on volume or flow-based settings, and that can collect composite or discrete samples. To obtain useful samples, it is critical that samples taken at different times be comparable. For example, in sampling a moving stream over the course of several weeks or seasons, the samples must be taken in proportion to the speed of the stream, which will fluctuate, in order to compare concentrations of sediments or contaminants during dry and wet periods. Without such proportional sampling, samples taken at different times under different stream flow speeds will not be comparable. Thus, flow proportional sampling results in few samples taken during low-flow (xe2x80x9cbaseflowxe2x80x9d) conditions and many samples during stormy conditions. This flow proportional sampling provides an accurate hydrograph which can be used to correlate constituent loads in relation to stream flow.
The present invention provides a flow proportional fluid sampler that pumps out a sample at a rate directly related to the flow speed. By linking pump speed to flow speed, samples taken during different fluid flow speeds are comparable. To accomplish this, a propeller or turbine is placed in the fluid to be sampled. The flow of the fluid drives the turbine. A pump is driven mechanically by the turbine. The pump draws a sample from the fluid and pumps it to a sample container. Since the turbine powers the pump, this system does not require an external power source to drive the pump. Since the pumping rate is directly related through the turbine to the fluid""s speed, there is no need for a separate mechanism to proportion the rate of sample collection to fluid speed. The present invention also provides a very simple electrical sensor to measure the speed of the fluid being tested, which may be recorded as part of the sample data. The present invention also provides a sample collection system to distribute and store samples taken at different times.
2. Discussion of the Prior Art
Sediment studies require frequent collection of suspended sediment at a test site. Site location, flow conditions, frequency of collection, and operational costs frequently make collection of sediment data by manual grab methods impractical. As a result several organizations, such as Federal Interagency Sedimentation Project (FISP), and United States Geological Survey (USGS), accompanied by commercial companies, have developed and evaluated several models of automated samplers. The USGS has identified seventeen optimum criteria for Automatic Pumping-Type Samplers in USGS Open-File Report 86-531, by Edwards and Glysson (1988):
1. Isokinetic sample collection if intake is aligned with approaching flow.
2. Suspended-sediment sample should be delivered from stream to sample container without a change in sediment concentration and particle-size distribution.
3. Cross contamination of sample caused by sediment carry-over in the system between sample-collection periods should be prevented.
4. Sampler should be capable of sediment collection when concentrations approach 50,000 (mg/l) and particle diameters reach 0.250 mm.
5. Sample-container volumes should be at least 350 ml.
6. The intake tube inside diameter should be xe2x85x9c or xc2xe inch, depending upon the size of the sampler used.
7. The mean velocity within the sampler plumbing should be great enough to ensure turbulent flow (Reynolds number greater than 4000 to ensure turbulent flow).
8. The sampler should be capable of vertical pumping lifts to 35 feet from intake to sample container.
9. The sampler should be capable of collecting a reasonable number of samples, dependent upon the purpose of sample collection and the flew conditions.
10. Some provision should be made for protection against freezing, evaporation, and dust contamination.
11. The sampler-container tray unit should be constructed to facilitate removal and transport as a unit.
12. The sampling cycle should be initiated in response to a timing device or stage change.
13. The capability of recording the sample collection date and time should exist.
14. The provision for operation using DC battery power or 110-volt AC power should exist.
15. The weight of the entire sampler or any one of its principal components should not exceed 100 pounds.
16. The maximum dimensions of the entire sampler or any one of its components should not exceed 35 inches in width or 79 inches in height.
17. The required floor area for the fully assembled sampler should not exceed 9 square feet (3 ft by 3 ft).
It is essential that the an automated sampler be able to meet the majority of the outline criteria. Automated samplers generally consist of: (1) a pump to draw a suspended-sediment from the stream flow, and, in some cases, back flush to prevent cross-contamination between samples, as well as to prevent freezing during winter months; (2) a sample container unit to hold sample bottles in position for filling; (3) a sample distribution system to divert a pumped sample to the correct bottle; (4) an activation system that starts and stops the sampling cycle, typically either at a regular time interval or in response to a rise in fall of the stream (gage height); and (5) an intake system through which samples are drawn from a point in the sampled cross section.
An advantage of automated samplers over grab sampling is that automated samplers can collect suspended-sediment samples during periods of rapid stage changes caused by storm-runoff events. Automated samplers also reduce the manpower necessary to carry out intensive sediment-collection programs. However, because of their mechanical complexity, power requirements, and limited sample capacity, automated samplers often require more frequent site visits than a conventional observer station. All the automated samplers use pumps powered by batteries or an AC power supply. This presents a significant problem in remote settings, where changing or recharging batteries is difficult. Batteries also add substantial weight to a sampler unit. Moreover, these units can be prone to freezing during cold weather.
Most automated samplers need a separate flow meter to correlate sampling to the test site""s flow, in order to provide flow proportional sampling. These systems are complicated and often require on-site calibration to ensure accuracy.
Sampling frequency for automatic sampling systems should be much greater at peak flows than during gradual base flows. High flows, such as those caused by a storm or spring runoff, typically contain high sediment concentrations. The peak sediment concentrations however do not usually coincide with the water-discharge peak. Therefore, a need for intermittent flow-proportional sampling is necessary to accurately depict the conditions within the steam environment.
Some of the automatic pump-type samplers are the U.S. PS-69, U.S. CS-fl, U.S. PS-82, Manning S-4050, and ISCO 1680. The U.S. PS-82 is the most recent design available from F.I.S.P. The Manning and ISCO samplers, frequently used by federal and state agencies, were developed by private companies. None of the current samplers meet all 17 of the optimum criteria set out above. The most critical of the shortcomings is that none of the samplers provide direct, proportional flow, or isokinetic, collection of samples. Examples of some sampler designs may be seen in U.S. Pat. No. 5,693,894, invented by Jobson (1997), and a technology intensive and costly sampler developed by Hungerford and Dickinson (1994), U.S. Pat. No. 5,299,141.
Therefore, one of the objects of this invention is to provide a sample collection device that takes flow proportional samples. Another object is to provide a sample pump that does not require battery or AC power. Another object is provide a flow velocity meter. Another object is provide constant pumping, in order to avoid freezing during cold weather. Another object is provide a light-weight, stand-alone sampler that is easy to manufacture. Another object is to provide a sampler that meets a majority of the USGS criteria.
The present invention meets these objects by providing a flow driven pump that uses the flow of the test site, such as a stream, to drive a pump, thereby eliminating the need for outside power for the pump. Because the pump is flow driven, it can run constantly, thereby inhibiting freezing and providing all weather suitability. The constant action of the pump also flushes the system, thereby preventing cross-contamination of samples taken at different times. The invention also incorporates a simple pulse counter that monitor""s the revolutions of the turbine propeller and can be used to measure velocity. The invention also provides a collection and distribution unit that can collect and store numerous samples in a small, light-weight container. Because the pump does not require battery power, the present invention can be left in the field for extended periods of time without maintenance.